Dinocampus coccinellae


Originally published in The Manitoban, 2011

Ah, time to go back to school. If you're anything like me you've probably bought a bunch of new pens and stationary you don't really need and have resolved to read your textbooks and class notes every day, maybe even get up extra early before classes to do something physically healthy. Soon enough though, as the first 2011 semester kicks into high gear, most of us are bound to feel as exhausted as though the life were being sucked right out of us. That's why I have chosen to begin the first fall issue of The Manitoban by telling you about the parasitic wasp Dinocampus coccinellae.
D. coccinellae is found throughout Eurasia and North America and parasitizes numerous species of lady beetles (your friendly, aphid-eating, garden variety “lady bug”). Females mate with males as infrequently as possible. A queen will store the sperm from a single mating for up to one year, using this sperm to fertilize eggs and produce sterile female workers which she uses to build her colony. When the sperm begins to run out, fertile males and females are produced and these disperse to form new colonies. 
Thus, males are rarer than females, although they are produced every once in awhile so they can disperse, mate, and contribute to the genetic diversity of the species via sexual reproduction.
The wasps preferentially parasitize female lady beetles and do so by injecting an egg directly into the beetle's body cavity. Once the egg hatches, the larva eats the lady beetle's own eggs in order to nourish itself and eliminate competition for nutrients. Once the eggs have all been eaten, the larva begins to eat it's lady beetle host's surrounding body tissue, including her reproductive structures.
After about 20 days the larva is ready to emerge. This is achieved by chewing a hole through the lady beetle's body. Then, the larva is ready to spin a coccoon inside which it will metamorphose into an adult wasp. The larva spins its coccoon within the hind limbs of the lady beetle, who is paralyzed, still alive and probably very miserable.
Currently unidentified venoms secreted by the wasp larva are believed to be responsible for the next stage in this ghastly business. The lady beetle, paralyzed with a wasp coccoon under her body, is now also a victim of behavioural modification courtesy of the wasp—the beetle begins to twitch and grasp erratically. This behaviour, along with the familiar red and black colouration of the lady beetle, serves to ward off predators, thus protecting the developing larva.
Many species of parasitic wasps lay eggs in a variety of host species; however, most of these lead to the death of the host. Not so with D. coccinellae, although I bet the lady beetles wish they were dead. After the adult wasp emerges from its coccoon, the effects of paralysis wear off, as does the behavioural control exerted by the larva. Approximately 25% of parasitized lady beetles survive this process and presumably amble off to continue their regular lady beetle duties, albeit with gored reproductive organs and a pretty wicked hole in the undercarriage.
Yet leaving the host alive is not without costs of its own. After all, nothing in life is truly free, right? Researchers at Laboratoire Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (CNRS/IRD/Université Montpellier) and the Université de Montréal were able to show that while wasp larvae guarded by lady beetles are less likely to experience predation, they also lay fewer eggs (Maure et al. 2011). The developing larvae lose resources by keeping the lady beetle alive, resulting in the observed reduction in fecundity of the adult wasps. Maure et al. (2011) showed that while larvae without lady beetle protection are more likely to experience predation, those that survive lay more eggs on average than wasps with a lady beetle bodyguard.
So when the term hits full swing remember—you don't have it half as bad as the spotted lady beetle does!





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